Insect repellent



Patented Feb. 24, 1942 g l I 1 INSECT REPELLENT Philip ,Granett, New Brunswick, N. J., assignor to National Carbon Company, Inc. a corporation of New York No Drawing. Application June 4, 1938, Serial No.

211,819. In Canada March 4, 1937 9 Claims. (01. 167-22) Preparations capable of repelling mosquitoes,

flies, gnats, fleas and other insect pests are genuinely valuable in the promotionof health and comfort. This invention is concerned with insect repellents, and its primary object is to provide compositions of improved effectiveness in repelling various insect pests, particularly mosquitoes.

I have found by test that insect repellent com-- positions of unusual emcacy can be made by employing as their essential ingredients certain esters of dicarboxylic, hydroxy dicarbbxylic, and hydroxy carboxylic aliphatic acids, each ester having a total of six to fifteen carbon atoms. It is preferred to select a substance of this class which is relatively non-volatile, or which has a boiling point above about 100 C., and those substances which have but slight odor, or which possess not unpleasant odors are most desirable. In general, the esters of lactic, malic and adipic acids are preferred, and specific esters of these acids which are useful in making the improved insect repellents are: ethylene glycol monoethyl ether lactate, tetrahydrofurfuryl lactate, benzyl lactate, diethyl dl-malate, dibutyl l-malate, dibutyl dl-malate, diethyl adipate,

dipropyl adipate,-dibutyl adipate and di(ethylene the repellent because on a dry type of skin these repellents sometimes tend to form a dry white layer two or three hours afterapplication. While this is in no way harmful, it is undesirable from the viewpoint of appearance.

Tests made against salt marsh mosquitoes (Aedes sollicitans) have shown that these compounds are on an average from two to ten times as effective repellents as oil of citronella, or from ten to fifteen times as effective as pine oil or the like. In particular, dibutyl dl-malate has shown an effective repellency of at least five to ten times that of oil of citronella.

Other insects, such as stable flies (Stomorys calcitrans) and strawberry or deer flies (chrysop spp.) have been repelled, but against such flies the period of repellency is considerably shorter than against mosquitoes. The species of insect against which protection is sought also influences results. The house mosquito (C. pizn'ens) bites only at dusk and at night and is relatively easy to repel as compared to the woodland mosquito (A. vexans), which bites during the day as well.

From observations in the field, the salt water as mosquitoes, house flies, stableflies, black fliesand fleas with a minimum of discomfort'to the user. The substances named are all relatively fumes may be incorporated. Preparations containing these materials may be placed directly in contact with the skin or clothing since they have,

in general, no irritating effect upon the skin or a slight reddening is sometimes caused by the malic acid esters, and the adipic acid esters may f produce a momentary smarting sensation. This is particularly true if the esters are applied undiluted. These compounds arenot greasy or oily in nature, and they may be easily washed oil. Because of their solvent nature they may have a cleansing effect on the skin, and they may tend ,to soften or dissolve paints and cosmetics with which the repellent come in contact. I

As a .rule, it is desirable to incorporate small amounts of certain inert materials, such as vegedeleterious action on fabrics. On sensitive skin marsh mosquitoes (A. sollicitans, A. cantator and A. taeniorhzmchus) are the fiercest biters and most diflicult to repel. They are also active during the day as well as at night.

, Although the better repellents are relatively non-volatile (boiling points usually being above about 100 C.) some degree of volatility is necessary to keep the insects, particularly mosquitoes, away from treated parts. Furthermore, odors perceptible to man do not, in themse1ves,-seem to influence mosquitoes to any marked extent.

For instance, the odor of citronella will persist long after its repellency has disappeared. -In-- tensity of odordoes not seem to aifect the insects either, for certain of the butyl compounds have very strong odors yet are not good repellents.

The compounds described may be applied, as such, to surfaces from which it is desired to repel the insect pests. They may also be applied as ingredients of lotions compounded with volatile diluents, such as ethanol, or less volatile materials, such as glycerol, or they may be mixed with one another. In general, dilution with inert materials reduces the effect of repellency of the compound. The repellents may be applied in combinations with various oily carriers, including vegetable oils, such as castor oil and peanut oil, and certain mineral oils. Unguents or creams Y containing the repellents, as well as powders or table or mineral oils, particularly corn oil, with .carriers of like nature may be effectively used.

In any of the difierent modes of application, it

No. 68,191 filed March 11, 1936.

- comprised of an inert diluent and dl'butyl 'dlmalate. I

3. An insect repellent composition which is comprised of an inert diluent and a repellent containing dibutyl dl-malate, said diluent con taining a vegetable oil.

4. An insect repellent composition which contains ethylene glycolmonoethyl ether lactate.

5. An insect repellent composition which contains d-lethyl adipate.

6. An insect repellent composition which .consists of an inert diluent and a repellent; said repellent consisting of at least one ester of a saturated'aliphatic acid or the group consisting of a dicarboxylic acid having six carbon atoms to the'molecule, a hydroxy dicarboxylic acid and a hydroxy monocarboxylic acid, said ester having at least six and not more than fifteen carbon atoms to the molecule, and the ester of said hy- Kdroxy monocarboxylic acid having an oxygen atom in ether linkage in the alcohol radical thereof when said alcohol radical contains not more than five carbon atoms.

7. An insect repellent composition which consists of an inert diluent and a repellent; said diluent containing an oil and said repellent con- 2,273,860 will be understood that mixtures or blends of the sisting of at least one ester of a saturated aliphatic acid of the group consisting of a dicarboxylic acid having six carbon atoms to the molecule, a hydroxy dicarboxylic acid and a hydroxy monocarboxylic acid, said ester having at least six and not more than fifteen carbon atoms to the molecule, and the ester of said hydroxy monocarboxylic acid having an oxygen atom in ether linkagein the alcohol radical thereof when said alcohol radical contains not more than five carbon atoms.

8. An insect repellent composition which consists of an inert diluent and a repellent; said diluent containing a vegetable oil and said repellent consisting of at least one'ester of a saturated aliphatic acid of the group consisting oi a dlcarboxylic acid having six carbon atoms to the molecule, a hydroxy dicarboxylic acid and a hydroxy monocarboxylic acid, said ester having at least six and not more than fifteen carbon atoms to the molecule, and the ester of said hydroxy monocarboxylic acid having an oxygen atom in ether linkage, in the alcohol radical thereof when said alcohol radical contains not more than five carbon atoms.

9. An insect repellent composition which contains as an essential activ ingredient at least one ester of a saturated aliphatic acid 01 the group consisting of a dicarboxylic acid having six carbon atoms to the molecule, a hydroxy dicarboxylic acid and a hydroxy monocarboxylic acid, said ester having at least six and not more than fifteen carbon atoms to the molecule, and the ester of said hydroxy monocarboxylic acid having an oxygen atom in ether linkage in the alcohol radical thereof when said alcohol radical contains not more than five carbon atoms.

Pm GRANETT. 

